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Intermittent fasting and keto diet: Can you do both at the same time?

Hint: Both lead to the same metabolic state.

Photo credit: Derek Owens via Unsplash
  • The keto diet and intermittent fasting are two weight-loss methods that have gained popularity in recent years.
  • Both can put the body in a state of ketosis, which leads to many of the same benefits.
  • However, scientists are still researching both intermittent fasting and the keto diet, and it's best to consult a doctor before making any drastic changes to your dietary habits – especially two changes at same time.

The keto diet and intermittent fasting are two popular, effective ways to lose weight quickly. Both methods bring upon similar changes in the body: more ketones, lower blood sugar and, at least anecdotally, improved mood and mental clarity. Both also call for less snacks, though the keto diet restricts which snacks you eat while intermittent fasting restricts when you snack.

It's generally safe to experiment with either the keto diet or intermittent fasting (though it's always better to consult a doctor first). But how safe is it to combine the two? First, let's take a look at what both of these weight-loss approaches do to the body, and how those processes might interact.

​The keto diet

In simple terms, ketosis is a metabolic process in which the body starts burning fat for fuel instead of sugar (glucose). Ketosis occurs naturally when the body doesn't have enough glucose to use as energy, so it instead turns to stored fats, which it converts into ketones that are distributed through blood to muscles and other tissue. The keto diet triggers this process by calling for a diet high in fat and low in carbohydrates, which results in lower levels of blood sugar and insulin.

Although scientists are still researching exactly how ketosis affects the body, some studies suggest keto diets can:

Cutting carbs is a sure way to put your body in a state of ketosis. Another way? Fasting.

​Intermittent fasting

Three square meals a day is the norm in the developed world, but in terms of human evolution it's a relatively new idea. The breakfast-lunch-dinner routine was likely established by Europeans, some of whom scoffed at the "uncivilized" Native Americans who didn't have rigid eating times and changed dietary habits with the seasons. But, as Yale University professor and author of Food: The History of Taste Paul Freedman argues, there's no biological reason for eating three meals a day at specific times.

Research shows that replacing rote eating habits with controlled fasting can be beneficial for your health, particularly through intermittent fasting, which can include fasting for several days at a time, fasting for 18 hours a day and eating only during the remaining six, and similar approaches.

Studies suggest intermittent fasting can:

One particularly interesting benefit of intermittent fasting is that it seems to be effective at increasing insulin sensitivity, which refers to how cells respond to insulin – the hormone that tells cells to allow sugar to enter so it can be used as fuel.

"The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream," Monique Tello, MD, MPH, wrote for Harvard Health Blog. "Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don't use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there."

But for reasons scientists don't completely understand, our cells can become resistant to insulin, which can cause your pancreas to produce too much of the hormone and then, after it becomes fatigued, not enough. Intermittent fasting might break that cycle by putting your body in a fasting state in which it doesn't overproduce insulin, as Dr. Jason Fung told the Bulletproof Radio podcast:

"If you become very insulin resistant, then your insulin levels are up all the time, your body is always trying to shove the energy into the fat cells, and then you feel cold and tired and lousy. That's the real problem. Resistance really depends on two things. It's not simply the high levels, but it's the persistence of those levels. What people have realized is that the insulin resistance, because it depends on those two things, a period of time where you can get your insulin levels very low is going to break that resistance because it breaks that persistence. Not simply the levels, but the persistence of those levels."

​Combining the keto diet with intermittent fasting

The major link between the keto diet and intermittent fasting is that they both can put the body into ketosis, generally resulting in lower levels of blood sugar and insulin, and therefore weight loss. But are they safe to do together?

Intermittent fasting will almost surely help you reach ketosis faster than a keto diet will alone, typically within 24 hours to three days. It's safe to say that, in terms of weight loss, combining these two approaches is likely to enhance the other's efficacy. But that's not to say everyone should do it.

Intermittent fasting and keto diets have been linked to mood problems in the weeks after beginning one or the other – irritability, anxiety, depressive symptoms. (For keto diets, this is often called the "keto flu.") It might be unsurprising that a drastic change in dietary habits would result in mood swings, and, to be sure, anecdotal reports suggest these symptoms tend to clear up eventually if people stick to their new routines. Still, it's best to consult your doctor before making such a drastic change – especially if you already suffer from a psychiatric condition, or a condition significantly affected by levels of blood sugar and insulin, like diabetes.

If you're going to move forward with combining intermittent fasting with the keto diet, consider these bits of advice from Perfect Keto:

"Make sure you still eat enough. Intermittent fasting does help you naturally eat less during the day, but be sure you're still eating nutritious ketogenic foods to avoid any deficiencies or metabolic issues. Use a website or app to calculate ideal caloric intake and your ketogenic macros for each day, then track them to make sure you're getting sufficient nutrition.

Measure your ketone levels. Even though fasting can really help you stay in ketosis, it's still important to make sure you aren't eating too many carbs or doing anything else to kick you out of ketosis. Track your ketones often to make sure you're actually in ketosis!"

Hulu's original movie "Palm Springs" is the comedy we needed this summer

Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.

Gear
  • Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
  • As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
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Two MIT students just solved Richard Feynman’s famed physics puzzle

Richard Feynman once asked a silly question. Two MIT students just answered it.

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Our ‘little brain’ turns out to be pretty big

The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
Mind & Brain
  • A powerful MRI combined with modeling software results in a totally new view of the human cerebellum.
  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

Economists show how welfare programs can turn a "profit"

What happens if we consider welfare programs as investments?

A homeless man faces Wall Street

Spencer Platt/Getty Images
Politics & Current Affairs
  • A recently published study suggests that some welfare programs more than pay for themselves.
  • It is one of the first major reviews of welfare programs to measure so many by a single metric.
  • The findings will likely inform future welfare reform and encourage debate on how to grade success.
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